This invention relates to a continuous DC control circuit and more particularly to a continuous DC control circuit employing a single potential source, a memory capacitor, and charge and discharge circuits having different time constants whereby a continuous DC control potential is provided.
Frequently, television receivers include a remote receiver and transmitter whereby specific functions of the receiver are remotely controlled. Usually, the receiver includes a plurality of frequency detectors which are individually activated in accordance with a transmitted signal at a given frequency.
In turn, the frequency detector initiates a control function by energizing or activating apparatus associated with the television receiver. For example, prior art remote control systems frequently employed bi-directional motors which were activated by a remote signal of a given frequency and mechanically altered the positional location of the adjustable arm of a potentiometer. In this manner, functions, such as volume for example, were readily adjusted by a remote control system.
In more recent apparatus the previously described and relatively expensive bi-directional motor systems were replaced by a charge storage and sampling means. Therein, a memory capacitor is employed to store a charge which is sampled to provide a continuous output potential in accordance with the charge which is, in turn, controlled by detection of a transmitted signal. Moreover, an example of one such system is disclosed in U.S. Pat. No. 3,637,922 issued to Gopal K. Srivastava and assigned to the assignee of the present application.
Although the above-described apparatus is an improvement over previously known techniques and extensively employed in numerous television receivers, it was found that the results were not completely satisfactory. Specifically, it was found that the memory capacitor tended to reach an undesirable level of charge during non-use of the apparatus whereupon a considerable period of time was required before proper operation of the apparatus was achieved upon reactivation of the apparatus.
One technique for reducing the undesired and extended period required to obtain proper operation of the apparatus after an extended period of non-use is disclosed in a U.S. Pat. application bearing Ser. No. 511,596 now U.S. Pat. No. 3,959,727 filed in the name of Dong Woo Rhee et al. Therein, a diode limiter is employed to restrict the level of charge accumulated on the memory capacitor whereupon the desired operation is achieved without an extended and undesired period of waiting for the applied energization to become effective.
Although the above-described apparatus and technique again provided improved results and is still extensively employed in television receivers, it has been found that room for improvement still exists. For example, the above apparatus requires a positive and a negative potential source which is expensive or at the very least inconvenient. Also, it has been found that the above apparatus has a restricted rate differential in so far as a different rate of charge and discharge of a given function is concerned.